Wednesday, August 24, 2011

yellow swallowtail

yellow swallowtail
sipping nectar from purple
thistle blossoms

Now here’s a dilemma. Prickly Canadian thistles are bursting into spiky purple blooms in our meadows, along the margins of roads and in cow pastures. The towering plants look like giant candelabras alight with lavender flames that attract butterflies, especially Fritillaries, but also Yellow Swallowtails. The entire thistle plant is covered with spikes that deter herbaceous animals from browsing on them, which is why farmers are not fond of them. Plus, they’re difficult to exterminate because they reproduce and spread easily, the bristly seeds clinging to animal fur, blown by the wind or dropped by birds. Thistle seeds are one of the favored foods of the American Goldfinch, which has a conical beak adapted to eating seed heads. The Goldfinch undergoes a complete molt in spring and autumn, the plumage of the male turning from winter's olive-brown to summer's lemon-yellow in order to attract the more modestly hued female. The finch's breeding season is tied to the peak supply of seeds in late summer. So what to do? Attempt to get rid of the thistles by frequent mowing, or let them proliferate in order to feed butterflies and finches? Well, there are plenty of thistles growing by the roadside and there are other flowers for butterflies and other seeds for finches. So I cut down any thistles I find growing in our meadows. Still, they are persistent and their deep roots keep them coming back year after year. Perhaps we should get some goats. It is true that they will eat just about anything, and I'm told they especially love the blossoms of Canadian thistles.

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